It is known that certain plastic materials have found some application in the ovenware field. For example, polymethylpentene has been used for injection molded trays which can be used in the preparation of foods. Polysulfone has also been employed in food handling applications. However, no satisfactory material has been found possessing utility over the wide ranges of conditions and of demands which are encountered in the provision of cook-in containers, or ovenware, which can be used in either thermal ovens or microwave ovens.
In addition to the obvious necessity for a material which can withstand the temperatures met in the heat source used for cooking, a material must provide a unique combination of a number of other characteristics before ovenware fabricated from the material can be successfully employed in the preparation of food. The material must have good electrical properties. It must be able to undergo severe thermal shocks in that ovenware prepared from it must be capable of going from conditions of extreme cold to high temperatures in relatively brief periods of time. The material must have good hardness and impact strength and possess high tensile and flexural strength. It must also be resistant to boiling water, food acids and fats and to adverse effects from immersion in detergents.
In the area of food related properties the material must impart to the ovenware fabricated from it resistance to staining by a wide variety of foodstuffs. It must provide a surface affording good antistick properties, ready releasability for the food which it contains. It must not emit or give off any volatile matter and it must not have any extractable constituent. And in addition to meeting all of the foregoing requirements, articles prepared from it must present a pleasing and generally uniform appearance in order to be marketable.